Pituitary hormones are prepared from ox, sheep, pig and human glands, and to a lesser degree from rat and dog glands. The preparations are of two grades: 1) suitable for experimental use in animals, carefully standardized for primary activity and for degree of contamination with other active principles; and 2) highly purified preparations suitable for use in radioimmunoassays or in tissue receptor assays. Hormones available are: Prolactin, Growth Hormone, Follicle-Stimulating Hormone, Luteinizing Hormone, Thyroid-Stimulating Hormone, (not of every species), and some special preparations such as relaxin, synthetic LH/FSH releasing hormone, and a number of specific antisera.